Nanotechnology can be defined as materials or devices engineered at the molecular level. Within this category are polymer nanocomposites, which are a class of materials that use molecular sized particles for reinforcing the polymer matrix, e.g. the reinforcing filler possesses one or more dimensions on a sub-micrometer scale. These materials blend an organoclay with polymer to produce a composite with equal or better physical and mechanical properties than their conventionally filled counterparts but at lower filler loadings.
Due to the surface area available with nano-fillers, polymer nanocomposites offer the potential for enhanced mechanical properties, barrier properties, thermal properties, and flame retardant properties when compared to conventionally filled materials.
One class of polymer nanocomposites uses a filler material that is based on the smectite class of aluminum silicate clays, a common representative of which is montmorillonite. Although naturally occurring and synthetic variations of this basic mineral structure can be used to make nanocomposites, the structure must allow the exchange of interlayer inorganic cations, such as Na+ or Ca2+, with organic cations, such as alkylammonium cations, if property enhancements are to be achieved. This replacement increases the spacing between the silicate sheets as well as improves the compatibility of the filler and the resin system, thereby facilitating exfoliation.
Recently, researchers have been investigating melt processing as a method for the preparation of nanocomposites for polyamide (nylon) and other thermoplastic systems such as polystyrene and polypropylene. These researchers have primarily been interested in the effect of the processing conditions on the physical and mechanical property enhancement or on the dispersion of the nanofiller as measured by transmission electron microscopy or x-ray diffraction. While these techniques are useful for evaluation on the sub-micrometer scale, little is found in the literature concerning the investigation of the dispersion of the nanofiller on a sub-millimeter scale, ie. a length scale that is on the edge of visual perception.
During processing of nanocomposite materials, it has been found that compaction of the nanofiller materials may occur. This agglomeration of the filler may affect the final properties of the composite by lowering the effective filler concentration and by the creation of stress risers around these agglomerates. Agglomerated filler further may cause an aesthetically displeasing surface. One example of a displeasing surface is shown in comparative FIG. 5.